2.5: Loops

Make sure that your drone is connected with Blockly before starting the lesson! If you are unsure of how to connect, go back to lesson 1.1 to review!

Loops let you repeat sections of your code. They’re a great shortcut — without them, you might have to connect the same blocks over and over again! Blockly has three different types of loops: 

• For loops will repeat the code inside them for the number of times you choose. There are two blocks that do this! 
• While loops will repeat the code inside them while a certain condition that you set is true.
• Until loops will repeat the code inside them until a certain condition that you set is true.

For loops repeat the code that’s inside them for the number of times that you choose. Once that code has been repeated for that amount of time, your program will exit out of the loop and move on to the next block.

Like we said in the first step, there are two for loop blocks in Blockly! One is the repeat block. To change the number in that block, you can just type in a new value. If you want to use a mathematical operation, equation, or variable, you can drag blocks from the math, logic, or variables menus to that gray area within the loop block.

The other for loop block is a little more complicated and looks more like what you would see in text-based coding. With the count block, you would name a variable, and then you would set it to start at one number and go up to another. You can also set how much you want the value to increase by.

Ready to try for loops out? Program your CoDrone EDU to look like it’s flying up a flight of stairs! The catch: since there are two different for loop blocks, you will need to write two different programs to try them out. Your CoDrone EDU should keep moving forward and up. The programs might look different to you, but what happens when you run them?

While loops repeat the code that’s inside them while the condition that you set is true. Each time the program runs through the while loop, it checks to see if the condition is true. If it is not, your program will exit the loop.

You had your drone fly in a shape in the variables lesson, but now you can try it with a loop! Set your variable to 0, and then have it increase by 1 every time in the while loop. While your variable is less than 4, program your CoDrone EDU to fly forward and then turn 90 degrees (or vice versa). 

Wondering why you’re starting at 0? Humans begin counting at 1, but computers begin counting at 0!

Until loops are a lot like while loops, except they’ll run the code inside the block until the condition is true. Each time the program runs through the while loop, it checks to see if the condition is true. If it is, the program will exit the loop, but after it finishes running that block of code one last time.

Set your variable to 0, and then have it increase by 1 every time in the until loop. Program your drone so that until your variable gets to 3, it will yaw to the left for 1.5 seconds.

Challenge: Ride the Wave

In this challenge, try programming your CoDrone EDU to fly in a wave shape. In other words, fly forward and repeat alternating the throttle to fly in a wave shape. Practice using loops with this challenge.

Challenge: Zigzag

Use loops to program your CoDrone EDU to fly in a zigzag shape. Fly forward and alternative positive and negative roll. Don’t forget to use loops!

In this loops lesson, you learned how to utilize loops with various commands. Loops can also be placed inside other loops, creating ‘nested’ loops that can repeat loops several times.